There's nothing in the NEC that says anything like that.

There's certainly nothing like that in the NC Plumbing code (based on the 2009 International Plumbing Code).

what is the deal with all this pipe tape wrapping then.

the inspectors are picky about having it wrapped on the exterior pipes where they exit the ground. For example you have to wrap the galvanized gas pipe or rigid electric pipe first a little underground and extend tape up, then back fill the dirt in so that the pipe is all wrapped up in the area where it exits the ground for a few inches.

See link for dewey, I found this says it references the 2003 IRC code chapter 24 that the city of Dewey published. It's a summary list of the code which requires underground gas pipe be wrapped with 10 Mil pvc pipe tape like what I linked earlier. 2 wraps half-lapped to get 40 mils required. And they want you to paint the pvc tape primer on the pipe first before taping it.

This is definitely the same as required in San Francisco so S.F. is not unique and it seems to be part of the IRC code so it's not a city specific thing. In the Home depot Pro store here in the plumbing dept, it's so used they carry both the pipe primer, and the required 10 Mil tape in large quantities. all the local plumbing stores carry it too.

http://www.dewey-humboldt.net/downloads/building/general/Gas Piping Installation.pdf

Can anyone confirm they are doing this for their exterior gas pipes in their area?

And also the Rigid Electric pipes exterior? I still can't find anything for NEC. And I still can't get a reference for wrapping copper pipe if it's near galvanized pipes.

I found a reference in this document for Electric where the government office of construction requires Rigid metal conduit pipe be taped with the 10 mil 2 times half lapped. Several references in this document require the 10 mil pvc tape on the rigid conduit. But I can't find the actual reference in NEC - just a lot of places where cities require it. See Link.
https://www.wbdg.org/ccb/VA/VAASC/VA 26 05 41.pdf

This post was edited by kisu on Sun, Jan 25, 15 at 23:47

Here is Portland, Oregon requiring the 10 mil on Rigid conduit. https://www.portlandoregon.gov/bes/article/53917

But I have no luck finding it in the NEC.

I found this NEMA article which talks about using 10 mil PVC tape to prevent corrosion of buried Rigid pipe, but does not give me the specific NEC article to reference. See section called Tape and shrink wraps.

https://www.nema.org/Technical/Documents/Bull_96_ULandNECRegforCorrosionProtofSteelConduit_03_09.pdf

This post was edited by kisu on Sun, Jan 25, 15 at 23:59

Exiting the ground I can understand but nobody has found anything that says anything about copper pipes and romex. I doubt it's any sort of thermal property. The NM sheath is good for over 90C and if your domestic hot water gets that hot, you've got big trouble.

This post was edited by ronnatalie on Mon, Jan 26, 15 at 10:17

The wrap of the copper pipes is for corrosion protection from concrete, masonry and soil chemicals. It is not part of the NEC. San Francisco-- who knows?

Why not ask the inspector why they require it? If he doesn't know he should know somebody who does. Actually if he doesn't know he isn't doing his job very well, but that's a different topic. :-]